Semiconductor nanocrystal particles and devices including the same

ABSTRACT

Disclosed are a semiconductor nanocrystal particle including indium (In), zinc (Zn), and phosphorus (P), wherein a mole ratio of the zinc relative to the indium is greater than or equal to about 25:1, and the semiconductor nanocrystal particle includes a core including a first semiconductor material including indium, zinc, and phosphorus and a shell disposed on the core and including a second semiconductor material including zinc and sulfur, a method of producing the same, and an electronic device including the same. The semiconductor nanocrystal particle emits blue light having a maximum peak emission at a wavelength of less than or equal to about 470 nanometers.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2017-0103127 filed in the Korean IntellectualProperty Office on Aug. 14, 2017, and all the benefits accruingtherefrom under 35 U.S.C. § 119, the entire content of which isincorporated herein by reference.

BACKGROUND 1. Field

A semiconductor nanocrystal particle and a device including the same aredisclosed.

2. Description of the Related Art

Physical characteristics (e.g., energy bandgaps) of nanoparticles thatare intrinsic characteristics of nanoparticles may be controlled bychanging their particle size, unlike bulk materials. For example,semiconductor nanocrystal particles also known as quantum dots are acrystalline material having a size of several nanometers. Suchsemiconductor nanocrystal particles have such a small size that theyhave a large surface area per unit volume and exhibit quantumconfinement effects, and thus have different properties from thecharacteristics of bulk materials having the same composition. Quantumdots may absorb light from an excitation source to be, e.g., and may be,excited, and may emit energy corresponding to an energy bandgap of thequantum dots.

Quantum dots may be synthesized using a vapor deposition method of metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE),and the like, a wet chemical method of adding precursor materials to anorganic solvent to grow crystals, and the like. In the wet chemicalmethod, organic compounds such as ligands/coordinating solvents may becoordinated on surfaces of nanocrystals to control a crystal growthduring the crystal growth.

In order to improve photoluminescence properties of quantum dots, acore-shell structure may be used, but core-shell quantum dots havingdesirable properties may be cadmium-based materials. Accordingly,desired is development of cadmium-free semiconductor nanocrystalparticles having desirable photoluminescence properties.

SUMMARY

An embodiment provides a cadmium-free semiconductor nanocrystal particlecapable of emitting blue light with improved efficiency.

Another embodiment provides a method of producing the semiconductornanocrystal particle.

Yet another embodiment provides an electronic device including thesemiconductor nanocrystal particle.

In an embodiment, a semiconductor nanocrystal particle includes indium(In), zinc (Zn), and phosphorus (P), wherein a mole ratio of zincrelative to indium is greater than or equal to about 25:1, and thesemiconductor nanocrystal particle includes a core including a firstsemiconductor material including indium, zinc, and phosphorus, and ashell disposed on the core and including a second semiconductor materialincluding zinc and sulfur.

The semiconductor nanocrystal particle may emit blue light having amaximum peak emission at a wavelength of less than or equal to about 470nanometers (nm).

The semiconductor nanocrystal particle may have quantum efficiency ofgreater than or equal to about 40%.

The semiconductor nanocrystal particle may have quantum efficiency ofgreater than or equal to about 45%.

The semiconductor nanocrystal particle may have quantum efficiency ofgreater than or equal to about 50%.

The mole ratio of the zinc relative to a mole amount of indium may begreater than or equal to about 29:1.

The mole ratio of the zinc relative to a mole amount of indium may begreater than or equal to about 29.5:1.

The mole ratio of the zinc relative to a mole amount of indium may begreater than or equal to about 30:1.

The semiconductor nanocrystal particle may have a mole ratio of sulfurrelative to indium of greater than or equal to about 18:1.

The semiconductor nanocrystal particle may have a mole ratio of sulfurrelative to indium of greater than or equal to about 25:1.

The semiconductor nanocrystal particle may have a mole ratio ofphosphorus relative to indium of less than about 1:1.

The semiconductor nanocrystal particle may have a mole ratio ofphosphorus relative to indium of less than or equal to about 0.85:1.

The core may include the zinc in a lattice of a zinc blend crystalstructure of InP.

The first semiconductor material may include InZnP.

The second semiconductor material may include ZnS.

The semiconductor nanocrystal particle may have an average size of lessthan or equal to about 4.5 nm.

The semiconductor nanocrystal particle may have an average size of lessthan or equal to about 4 nm.

The core may have a size of less than or equal to about 2 nm.

The shell may not include selenium.

The semiconductor nanocrystal particle may emit blue light having amaximum peak emission of the blue light may be present at a wavelengthof about 440 nm to about 470 nm.

The semiconductor nanocrystal particle may have quantum efficiency ofgreater than or equal to about 45%.

The semiconductor nanocrystal particle may have quantum efficiency ofgreater than or equal to about 50%.

The maximum peak emission of the blue light may have a full width athalf maximum (FWHM) of less than or equal to about 60 nm.

In an embodiment, a method of producing a cadmium-free semiconductornanocrystal particle emitting blue light includes heating a firstsolution including an indium precursor, a first zinc precursor, a firstorganic ligand, and a first organic solvent at a first temperature ofgreater than or equal to about 100° C. and less than about 180° C.;

adding a phosphorus precursor to the first solution to obtain a secondsolution;

heating the second solution at a second temperature of greater than orequal to about 180° C. and less than or equal to about 260° C. tosynthesize a core including a first semiconductor material, the firstsemiconductor material including indium, phosphorus, and zinc;

separating the core from the second solution;

heating a third solution including a second zinc precursor, a secondorganic ligand, and a second organic solvent to a third temperature thatis less than a shell-forming temperature, to obtain a heated thirdsolution;

adding the core and a sulfur precursor to the heated third solution toobtain a fourth solution; and

heating the fourth solution at a shell-forming temperature to form ashell including a second semiconductor material including zinc andsulfur, on the core.

The indium precursor may include indium acetate, alkylated indium (e.g.,trimethyl indium), indium hydroxide, indium chloride, indium oxide,indium nitrate, indium sulfate, or a combination thereof.

The first zinc precursor and the second zinc precursor may be the sameor different and may independently include a Zn metal powder, ZnO, analkylated Zn compound, a Zn alkoxide, a Zn carboxylate, a Zn nitrate, aZn perchlorate, a Zn sulfate, a Zn acetylacetonate, a Zn halide, a Zncyanide, a Zn hydroxide, or a combination thereof.

The first organic ligand and the second organic ligand may be the sameor different and may independently include RCOOH, RNH₂, R₂NH, R₃N, RSH,RH₂PO, R₂HPO, R₃PO, RH₂P, R₂HP, R₃P, ROH, RCOOR′, RPO(OH)₂, RHPOOH,R₂POOH, or a combination thereof, wherein R and R′ independently includea substituted or unsubstituted C1 to C40 (or to C24) aliphatichydrocarbon, a substituted or unsubstituted C6 to C20 aromatichydrocarbon, or a combination thereof.

The phosphorus precursor may include tris(trimethylsilyl) phosphine,tris(dimethylamino) phosphine, triethylphosphine, tributylphosphine,trioctylphosphine, triphenylphosphine, tricyclohexylphosphine, or acombination thereof.

In the first solution, a mole ratio of the first zinc precursor relativeto the indium precursor may be greater than or equal to about 1.7:1.

The first solution may not include dodecane thiol.

The first ligand may include an amine compound.

The semiconductor nanocrystal particle may include indium (In), zinc(Zn), and phosphorus (P) and a mole ratio of zinc relative to indiumgreater than or equal to about 25:1.

The semiconductor nanocrystal particle may emit blue light having amaximum peak emission at a wavelength of less than or equal to about 470nm.

The semiconductor nanocrystal particle may have quantum efficiency ofgreater than or equal to about 40%.

In an embodiment, an electronic device includes

a first electrode and a second electrode facing each other; and

a quantum dot emission layer disposed between the first electrode andthe second electrode, the quantum dot emission layer including aplurality of semiconductor nanocrystals, wherein the plurality ofsemiconductor nanocrystals includes the semiconductor nanocrystalparticle.

The electronic device may include an auxiliary layer including (e.g.,crystalline) ZnO (e.g., nanoparticles) between the first electrode andthe quantum dot emission layer or between the second electrode and thequantum dot emission layer.

An indium-based semiconductor nanocrystal particle capable of emittingblue light is provided. The semiconductor nanocrystal particle may beapplied to various display devices, biolabeling (biosensor, bioimaging),a photodetector, a solar cell, a polymer composite, an organic/inorganichybrid composite, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross-section of an electronic device accordingto a non-limiting embodiment.

FIG. 2 shows a schematic cross-section of an electronic device accordingto a non-limiting embodiment.

FIG. 3 shows a schematic cross-section of an electronic device accordingto a non-limiting embodiment.

FIG. 4 shows a schematic cross-section of an electronic device accordingto a non-limiting embodiment.

FIG. 5 shows ultraviolet-visible (UV-Vis) absorption spectra ofabsorption intensity (arbitrary units (a.u.)) versus wavelength (nm) ofthe semiconductor nanocrystal particles produced in Examples andComparative Examples.

FIG. 6 shows PL spectra of PL intensity ((a.u.) versus wavelength (nm)of the semiconductor nanocrystal particles produced in Examples andComparative Examples.

FIG. 7 shows a transmission electron microscope image of thesemiconductor nanocrystal particle produced in Example.

FIG. 8 shows a size distribution of counts (number (#)) versus diameter(nm) of the semiconductor nanocrystal particle produced in Example.

FIG. 9 is a schematic cross-sectional view showing the device (normalstructure) manufactured in Example 3.

FIG. 10 shows an electro-luminescence property of current density(milliamperes per square centimeter (mA/cm²)) versus voltage (volts (V))of the device manufactured in Example 3.

FIG. 11 shows an electro-luminescence property of luminescence (candelasper square centimeter (cd/cm²)) versus voltage (V) of the devicemanufactured in Example 3.

FIG. 12 shows an electro-luminescence property of External QuantumEfficiency (EQE) (percent (%)) versus luminescence (cd/cm²) of thedevice manufactured in Example 3.

FIG. 13 shows an electro-luminescence property of intensity (a.u.)versus wavelength (nm) of the device manufactured in Example 3.

FIG. 14 is a schematic cross-sectional view showing the device (invertedstructure) manufactured in Example 4.

FIG. 15 shows an electro-luminescence property of current density(mA/cm²) versus voltage (V) of the device manufactured in Example 4.

FIG. 16 shows an electro-luminescence property of luminescence (cd/m²)versus voltage (V) of the device manufactured in Example 4.

FIG. 17 shows an electro-luminescence property of EQE (%) versusluminescence (cd/cm²) of the device manufactured in Example 4.

FIG. 18 shows an electro-luminescence property of intensity (a.u.)versus wavelength (nm) of the device manufactured in Example 4.

DETAILED DESCRIPTION

Advantages and characteristics of this disclosure, and a method forachieving the same, will become evident referring to the followingexample embodiments together with the drawings attached hereto. However,the embodiments should not be construed as being limited to theembodiments set forth herein. If not defined otherwise, all terms(including technical and scientific terms) in the specification may bedefined as commonly understood by one skilled in the art. The termsdefined in a generally-used dictionary may not be interpreted ideally orexaggeratedly unless clearly defined. In addition, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof stated elements but not the exclusion of any other elements.

Further, the singular includes the plural unless mentioned otherwise.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification.

It will be understood that when an element such as a layer, film,region, or substrate is referred to as being “on” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “At least one” is not to be construed as limiting “a” or“an.” “Or” means “and/or.” As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

“About” as used herein is inclusive of the stated value and means withinan acceptable range of deviation for the particular value as determinedby one of ordinary skill in the art, considering the measurement inquestion and the error associated with measurement of the particularquantity (i.e., the limitations of the measurement system). For example,“about” can mean within one or more standard deviations, or within ±10%,or 5% of the stated value.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, as used herein, when a definition is not otherwiseprovided, “substituted” refers to replacement of hydrogen of a compoundor a corresponding moiety with a 01 to C30 alkyl group, a C2 to C30alkenyl group, a C2 to C30 alkynyl group, a C6 to C30 aryl group, a C7to C30 alkylaryl group, a 01 to C30 alkoxy group, a 01 to C30heteroalkyl group, a C3 to C30 heteroalkylaryl group, a C3 to C30cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C30cycloalkynyl group, a C2 to C30 heterocycloalkyl group, a halogen (—F,—Cl, —Br, or —I), a hydroxy group (—OH), a nitro group (—NO₂), a cyanogroup (—CN), an amino group (—NRR′ wherein R and R′ independentlyinclude hydrogen or a C1 to C6 alkyl group), an azido group (—N₃), anamidino group (—C(═NH)NH₂), a hydrazino group (—NHNH₂), a hydrazonogroup (═N(NH₂)), an aldehyde group (—C(═O)H), a carbamoyl group(—C(O)NH₂), a thiol group (—SH), an ester group (—C(═O)OR, wherein R isa C1 to C6 alkyl group or a C6 to C12 aryl group), a carboxyl group(—COOH) or a salt thereof (—C(═O)OM, wherein M is an organic orinorganic cation), a sulfonic acid group (—SO₃H) or a salt thereof(˜SO₃M, wherein M is an organic or inorganic cation), a phosphoric acidgroup (—PO₃H₂) or a salt thereof (˜PO₃MH or —PO₃M₂, wherein M is anorganic or inorganic cation), or a combination thereof.

Herein, a hydrocarbon group refers to a group including carbon andhydrogen (e.g., alkyl, alkenyl, alkynyl, or aryl group). The hydrocarbongroup may be a group having a monovalence or greater formed by removalof one or more hydrogen atoms from, alkane, alkene, alkyne, or arene. Inthe hydrocarbon group, at least one methylene may be replaced with anoxide moiety, a carbonyl moiety, or a combination thereof.

Herein, the term aliphatic refers to a saturated or unsaturated linearor branched hydrocarbon group. An aliphatic group may be an alkyl,alkenyl, or alkynyl group, for example.

Herein, the term aromatic refers to an organic compound or groupcomprising at least one unsaturated cyclic group having delocalized pielectrons. The term encompasses both hydrocarbon aromatic compounds andheteroaromatic compounds.

Herein, the term alkyl refers to a linear or branched saturatedmonovalent hydrocarbon group (methyl, ethyl, hexyl, etc.).

Herein, the term alkenyl refers to a linear or branched monovalenthydrocarbon group having one or more carbon-carbon double bond.

Herein, the term alkynyl refers to a linear or branched monovalenthydrocarbon group having one or more carbon-carbon triple bond.

Herein, the term aryl refers to a group formed by removal of at leastone hydrogen from an aromatic group (e.g., a phenyl or a naphthylgroup).

Herein, the term hetero refers to inclusion of 1 to 3 heteroatoms thatare N, O, S, Si, P, or a combination thereof.

If not defined otherwise, alkyl refers to a C1 to C20 alkyl, or a C1 toC12 alkyl, or a C1 to C6 alkyl.

As used herein, the term “group” refers to a group of Periodic Table.

A semiconductor nanocrystal particle (hereinafter, referred to a quantumdot) may absorb light from an excitation source and may emit energycorresponding to their energy bandgap. For example, as the size of aquantum dot increases, the quantum dot may have narrow energy bandgapsand increased light emitting wavelengths. A semiconductor nanocrystalhas drawn attention as a light emitting material in various fields suchas in a display device, an energy device, or a bio light emittingdevice.

Quantum dots having photoluminescence properties at an applicable levelmay be based on cadmium (Cd). Cadmium may cause severeenvironment/health problems and a restricted element by Restriction ofHazardous Substances Directive (RoHS) in a plurality of countries.Accordingly, desired is development of a cadmium-free quantum dot havingimproved photoluminescence properties. An indium phosphide-based quantumdot as an alternative material may replace a cadmium-based quantum dot.A cadmium-based quantum dot may exhibit better performance than anInP-based quantum dot (e.g., photoluminescence properties such as alight emitting wavelength, luminous efficiency, and the like). Forexample, it has been difficult to develop an InP-based quantum dotemitting light having a maximum peak emission at a wavelength of lessthan or equal to about 470 nm (or less than about 470 nm) with improvedquantum efficiency (e.g., greater than or equal to about 40%).

An indium phosphide-based semiconductor nanocrystal particle accordingto an embodiment has a structure and a composition which will bedescribed later and may emit blue light with improved efficiency.

In an embodiment, a semiconductor nanocrystal particle includes indium(In), zinc (Zn), and phosphorus (P). The particle includes a coreincluding a first semiconductor material including indium, zinc, andphosphorus and a shell disposed on the core and including a secondsemiconductor material including zinc and sulfur. The semiconductornanocrystal particle emits blue light having a maximum peak emission ata wavelength of less than or equal to about 470 nm.

In the semiconductor nanocrystal particle, a mole ratio of the zincrelative to the indium may be greater than or equal to about 25:1. In anembodiment, the mole ratio of the zinc relative to the indium may begreater than or equal to about 28:1, greater than or equal to about29:1, or greater than or equal to about 30:1. The mole ratio of the zincrelative to the indium may be less than or equal to about 55:1, forexample, less than or equal to about 50:1, less than or equal to about45:1, less than or equal to about 40:1, less than or equal to about35:1, less than or equal to about 34:1, less than or equal to about33:1, or less than or equal to about 32:1. Without wishing to be boundby any particular theory, the aforementioned composition may contributeto a blue light emission of the semiconductor nanocrystal particle withimproved efficiency. The mole ratio may be confirmed by an appropriatemeans such as an inductively coupled plasma-atomic emission spectroscopy(ICP-AES), an energy disperse X-ray spectroscopy (EDS), or the like.

In the semiconductor nanocrystal particle, the mole ratio of sulfurrelative to indium may be greater than or equal to about 18:1, forexample greater than or equal to about 20:1, greater than or equal toabout 21:1, greater than or equal to about 22:1, greater than or equalto about 23:1, greater than or equal to about 24:1, greater than orequal to about 25:1, or greater than or equal to about 26:1. In thesemiconductor nanocrystal particle, the mole ratio of the sulfurrelative to the indium may be less than or equal to about 60:1, forexample, less than or equal to about 50:1, less than or equal to about45:1, less than or equal to about 40:1, less than or equal to about35:1, less than or equal to about 30:1, less than or equal to about29:1, less than or equal to about 28:1, or less than or equal to about27:1. In the semiconductor nanocrystal particle, a mole ratio ofphosphorus relative to indium may be less than about 1:1. For example,in the semiconductor nanocrystal particle, the mole ratio of thephosphorus relative to the indium may be less than or equal to about0.87:1, less than or equal to about 0.86:1, less than or equal to about0.85:1, less than or equal to about 0.84:1, less than or equal to about0.83:1, or less than or equal to about 0.82:1. In the semiconductornanocrystal particle, a mole ratio of phosphorus relative to indium maybe greater than or equal to about 0.2:1, for example, greater than orequal to about 0.3:1, greater than or equal to about 0.4:1, or greaterthan or equal to about 0.5:1. The semiconductor nanocrystal particle maynot include cadmium.

In the core/shell structure, the first semiconductor material mayinclude InZnP. The core may not include sulfur.

In the core/shell structure, the second semiconductor material mayinclude ZnS. For example, the shell may not include selenium. The shellmay be a multi-layered shell including a plurality of layers. In theplurality of layers, adjacent layers may include semiconductor materialshaving different compositions. The shell may be a gradient alloy havinga concentration changing along with a radial direction.

The semiconductor nanocrystal particle may have any suitable shape thatis not particularly limited. The shape of the semiconductor nanocrystalmay include a spherical shape, an ellipsoid shape, a pyramid shape, acube shape, a rectangular parallelepiped shape, a polyhedron shape, amultipod shape, or a combination thereof, but is not limited thereto.

An average size of the semiconductor nanocrystal particle may be lessthan or equal to about 4.5 nm, for example, less than or equal to about4.3 nm, less than or equal to about 4.2 nm, less than or equal to about4.1 nm, or less than or equal to about 4 nm. An average size of thesemiconductor nanocrystal particle may be greater than or equal to about2.5 nm, greater than or equal to about 2.6 nm, greater than or equal toabout 2.7 nm, greater than or equal to about 2.8 nm, greater than orequal to about 2.9 nm, greater than or equal to about 3 nm, greater thanor equal to about 3.1 nm, greater than or equal to about 3.2 nm, greaterthan or equal to about 3.3 nm, or greater than or equal to about 3.4 nm.A size of the core may be less than or equal to about 2 nm, for example,less than or equal to about 1.9 nm, less than or equal to about 1.8 nm,or less than or equal to about 1.7 nm. The size of the core may begreater than or equal to about 1 nm, for example, greater than or equalto about 1.1 nm, greater than or equal to about 1.2 nm, greater than orequal to about 1.3 nm, greater than or equal to about 1.4 nm, or greaterthan or equal to about 1.5 nm. The core size may be calculated from anultraviolet (UV) first absorption wavelength. Without wishing to bebound by any particular theory, within the ranges of the core size, thesemiconductor nanocrystal according to an embodiment may exhibitdesirable photoluminescence properties. A thickness of the shell may begreater than or equal to about 1 nm, for example, greater than about 1nm, greater than or equal to about 1.1 nm, greater than or equal toabout 1.2 nm, greater than or equal to about 1.3 nm, greater than orequal to about 1.4 nm or greater than or equal to about 1.5 nm. Thethickness of the shell may be less than or equal to about 3 nm, forexample, 2.9 nm, less than or equal to about 2.8 nm, less than or equalto about 2.7 nm, less than or equal to about 2.6 nm, less than or equalto about 2.5 nm, less than or equal to about 2.4 nm, less than or equalto about 2.3 nm, less than or equal to about 2.2 nm, less than or equalto about 2.1 nm, less than or equal to about 2.0 nm, less than or equalto about 1.9 nm, or less than or equal to about 1.8 nm.

Without wishing to be bound by any particular theory, within the rangesof the core size, the semiconductor nanocrystal according to anembodiment may exhibit desirable photoluminescence properties. As usedherein, the size of the semiconductor nanocrystal may be a diameter.When the particle has a polygonal or multipod shape, the size of theparticle may be a diameter calculated from a two dimensional areadetermined in an electron microscopic analysis.

The semiconductor nanocrystal particle according to an embodiment mayemit blue light having a maximum peak emission at a wavelength ofgreater than or equal to about 430 nm (e.g., greater than or equal toabout 440 nm, greater than or equal to about 450 nm, greater than orequal to about 451 nm, greater than or equal to about 452 nm, greaterthan or equal to about 453 nm, greater than or equal to about 454 nm,greater than or equal to about 455 nm, greater than or equal to about456 nm, greater than or equal to about 457 nm, greater than or equal toabout 458 nm, greater than or equal to about 459 nm, or greater than orequal to about 460 nm) and less than or equal to about 470 nm (e.g.,less than about 470 nm, less than or equal to about 468 nm, less than orequal to about 467 nm, less than or equal to about 466 nm, or less thanor equal to about 465 nm). The blue light may have a maximum lightemitting peak wavelength of about 452 nm to about 468 nm. The maximumpeak emission may have a full width at half maximum (FWHM) of less thanor equal to about 65 nm, for example, less than or equal to about 63 nm,less than or equal to about 62 nm, less than or equal to about 61 nm, orless than or equal to about 60 nm.

The semiconductor nanocrystal may have quantum efficiency of greaterthan or equal to about 40%, for example, greater than or equal to about41%, greater than or equal to about 42%, greater than or equal to about43%, greater than or equal to about 44%, greater than or equal to about45%, greater than or equal to about 46%, greater than or equal to about47%, greater than or equal to about 48%, greater than or equal to about49%, and greater than or equal to about 50%. The semiconductornanocrystal may have quantum efficiency of greater than or equal toabout 80%, greater than or equal to about 90%, greater than or equal toabout 95%, greater than or equal to about 99%, or 100%.

The semiconductor nanocrystal particle includes an organic ligand bondedon, e.g., to, the surface of the semiconductor nanocrystal particle, andthe ligand may include an amine compound and a carboxylic acid compound.The organic ligand is illustrated in detail hereinafter.

In order to manufacture an electro-luminescent quantum dot-based device,a quantum dot having a central, e.g., maximum peak, light emittingwavelength of less than or equal to about 470 nm, for example, less thanabout 470 nm, and less than or equal to about 465 nm may be desired. Acadmium-based quantum dot may have such a central light emittingwavelength (i.e., a light emitting peak wavelength) within the ranges,and may cause a serious environmental/contamination problem asaforementioned. Accordingly, a cadmium-free quantum dot having a centrallight emitting wavelength within the above ranges may be synthesized inorder to realize the next generation display, a quantum dot (QD) lightemitting diode (LED) device.

A type of cadmium-free quantum dot, an InP-based quantum dot, has asmall bandgap compared with a cadmium-based quantum dot such as aCdSe-based one. Accordingly, an InP-based quantum dot desirably has asmaller particle size to emit blue light. However, small particle-sizedsemiconductor nanocrystals may not easily be uniformly dispersed.Accordingly, it may be more difficult for an InP-based quantum dot toemit blue light as compared to a cadmium-based quantum dot. An indiumphosphide-based quantum dot emitting blue light of a short wavelength ofless than or equal to about 470 nm with efficiency applicable to adevice may be desirable.

The InP may have a zinc blend crystal lattice, and the zinc in the coremay be included in the zinc blend crystal lattice of the InP.

The indium phosphide-based quantum dot according to an embodiment mayshow photoluminescence properties in desired ranges (e.g., a centrallight emitting wavelength of less than or equal to about 470 nm, forexample, less than about 470 nm and less than or equal to about 465 nmand luminous efficiency of greater than or equal to about 40%) and thuscontribute to manufacturing various electronic devices, for example, aquantum dot LED device.

A method of producing the semiconductor nanocrystal particle accordingto an embodiment includes heating a first solution including an indiumprecursor, a first zinc precursor, a first organic ligand, and a firstorganic solvent at a first temperature.

The indium precursor may include indium acetate, indium hydroxide,indium chloride, indium oxide, indium nitrate, indium sulfate, trimethylindium, or a combination thereof.

The first zinc precursor may include a Zn metal powder, ZnO, zincperoxide, an alkylated Zn compound (e.g., a C2 to C30 dialkyl zinc suchas dimethyl zinc or diethyl zinc), a Zn carboxylate (e.g., a zincacetate), a Zn dithiocarbamate, a zinc carbonate, a Zn nitrate, a Znperchlorate, a Zn sulfate, a Zn acetylacetonate, a Zn halide (e.g., azinc chloride, etc.), a Zn cyanide, a Zn hydroxide, a zinc perchlorate,or a combination thereof.

The first organic solvent may desirably be a coordinating solvent andnon-coordination solvent. Examples of the organic solvent may include aC6 to C22 primary amine such as hexadecylamine, a C6 to C22 secondaryamine such as a dioctylamine, a C6 to C40 tertiary amine such as atrioctyl amine, a nitrogen-containing heterocyclic compound such aspyridine, a C6 to C40 olefin such as octadecene, a C6 to C40 aliphatichydrocarbon such as hexadecane, octadecane, or squalane, an aromatichydrocarbon substituted with a C6 to C30 alkyl group such asphenyldodecane, phenyltetradecane, or phenyl hexadecane, a primary,secondary, or tertiary phosphine (e.g., trioctyl phosphine) substitutedwith at least one (e.g., 1, 2, or 3) C6 to C22 alkyl groups, a phosphineoxide (e.g., trioctylphosphine oxide) substituted with at least one(e.g., 1, 2, or 3) C6 to C22 alkyl groups, a C12 to C22 aromatic ethersuch as a phenyl ether, a benzyl ether, or a combination thereof, butare not limited thereto.

The first organic ligand (and/or the second organic ligand that will bedescribed later) may coordinate the surface of the produced nanocrystaland may have an effect on the light emitting and electriccharacteristics, and may also well-disperse the nanocrystal in thesolution phase. The organic ligand may include RCOOH, RNH₂, R₂NH, R₃N,RSH, RH₂PO, R₂HPO, R₃PO, RH₂P, R₂HP, R₃P, ROH, RCOOR′, RPO(OH)₂, RHPOOH,R₂POOH (wherein, R and R′ independently include a C1 to C24 substitutedor unsubstituted aliphatic hydrocarbon, or a C6 to C20 substituted orunsubstituted aromatic hydrocarbon, or a combination thereof), or acombination thereof. The ligand may be may be used alone or in a mixtureof two or more compounds.

Examples of the first organic ligand may be methane thiol, ethane thiol,propane thiol, butane thiol, pentane thiol, hexane thiol, octane thiol,dodecane thiol, hexadecane thiol, octadecane thiol, benzyl thiol;methane amine, ethane amine, propane amine, butane amine, pentane amine,hexane amine, octane amine, dodecane amine, hexadecyl amine, oleylamine, octadecyl amine, dimethyl amine, diethyl amine, dipropyl amine;methanoic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoicacid, hexanoic acid, heptanoic acid, octanoic acid, dodecanoic acid,hexadecanoic acid, octadecanoic acid, oleic acid, benzoic acid, palmiticacid, stearic acid; a phosphine such as methyl phosphine, ethylphosphine, propyl phosphine, butyl phosphine, pentyl phosphine,tributylphosphine, or trioctylphosphine; diphenyl phosphine; a triphenylphosphine compound such as triphenyl phosphine; a phosphine oxide suchas methyl phosphine oxide, ethyl phosphine oxide, propyl phosphineoxide, butyl phosphine oxide, diphenyl phospine oxide, trioctylphosphineoxide, or triphenyl phosphine oxide; or phosphonic acid, but are notlimited thereto. The organic ligand compound may be used alone or in amixture of two or more compounds.

In order to form the core, an amount of the first zinc precursor may begreater than or equal to about 1.7 moles (mol), for example, greaterthan or equal to about 1.8 mol, greater than or equal to about 1.9 mol,greater than or equal to about 2.0 mol, greater than or equal to about2.1 mol, greater than or equal to about 2.2 mol, greater than or equalto about 2.3 mol, greater than or equal to about 2.4 mol, greater thanor equal to about 2.5 mol, greater than or equal to about 2.6 mol,greater than or equal to about 2.7 mol, greater than or equal to about2.8 mol, greater than or equal to about 2.9 mol, or greater than orequal to about 3 mol, based on 1 mol of the indium precursor. In orderto form the core, an amount of the first zinc precursor may be less thanor equal to about 10 mol, for example, less than or equal to about 9mol, less than or equal to about 8 mol, less than or equal to about 7mol, less than or equal to about 6 mol, or less than or equal to about 5mol, based on 1 mol of the indium precursor. With these amounts, thecore having the composition described above may be formed. In order toform the core, an amount of the first organic ligand may be greater thanor equal to about 6 mol, for example, greater than about 6 mol, greaterthan or equal to about 6.5 mol, greater than or equal to about 7 mol andless than or equal to about 20 mol, for example, less than or equal toabout 15 mol, less than or equal to about 14 mol, less than or equal toabout 13 mol, less than or equal to about 12 mol, less than or equal toabout 11 mol, or less than or equal to about 10 mol based on 1 mol ofIn. A concentration of each component in the first solution may beappropriately selected and is not particularly limited.

The first temperature may be greater than or equal to about 100° C.,greater than or equal to about 110° C., and less than about 180° C.Without wishing to be bound by any particular theory, the abovetemperature range may contribute to obtaining a desired coresize/composition. The first solution may be heated for an appropriatelyselected time. For example, the first solution may be heated for greaterthan or equal to about 5 minutes, for example, greater than or equal toabout 10 minutes, greater than or equal to about 15 minutes, greaterthan or equal to about 20 minutes, and greater than or equal to about 25minutes but less than or equal to about 80 minutes and, for example,less than or equal to about 70 minutes but is not limited thereto.

Subsequently, a phosphorus precursor is added to the first solution(e.g., an input) to obtain a second solution, and the second solution isreacted at a second temperature (a core-forming temperature) tosynthesize a core including a first semiconductor material includingindium, phosphorus, and zinc.

The phosphorus precursor may include tris(trimethylsilyl) phosphine,tris(dimethylamino) phosphine, triethylphosphine, tributylphosphine,trioctylphosphine, triphenylphosphine, tricyclohexylphosphine, or acombination thereof, but is not limited thereto.

An amount of each component in the second solution may be appropriatelyselected by considering, e.g., based on, a composition/property and thelike of a semiconductor nanocrystal. The first solution and the secondsolution may not include dodecanethiol.

The core-forming temperature may be appropriately selected from rangesof greater than or equal to about 180° C., for example, greater than orequal to about 190° C. and less than or equal to about 260° C., forexample, less than or equal to about 250° C., less than or equal toabout 240° C., less than or equal to about 230° C., less than or equalto about 220° C., or less than or equal to about 210° C. Time forforming the core may be appropriately selected by considering, e.g.,based on, a core-forming temperature and a core size. For example, thecore-forming time may be greater than or equal to about 1 minute,greater than or equal to about 2 minutes, greater than or equal to about3 minutes, greater than or equal to about 4 minutes, and greater than orequal to about 5 minutes but for example less than or equal to about 30minutes, less than or equal to about 25 minutes, less than or equal toabout 20 minutes, and less than or equal to about 15 minutes but is notlimited thereto. The core including the first semiconductor material isthe same as described above. The size of the core may be adjusted bycontrolling the reaction temperature and the reaction time. The core mayhave a first absorption maximum UV wavelength of about 350 nm, forexample, greater than or equal to about 365 nm and less than or equal toabout 400 nm, and for example, less than or equal to about 370 nm.

After the reaction, a non-solvent is added to the second solutioncontaining the core to separate the core from the second solution. Theseparated core may be dispersed in an organic solvent (e.g., mixablewith the above first organic solvent or a second organic solvent to bedescribed below).

Subsequently, a fourth solution is obtained by heating a third solutionincluding a second zinc precursor, a second organic ligand, and a secondorganic solvent at a third temperature of less than a shell-formingtemperature and adding the core and a sulfur precursor to the heatedthird solution.

The second zinc precursor, the second organic ligand, and the secondorganic solvent are substantially the same as the first zinc precursor,the first organic ligand, and the first organic solvent. The secondorganic ligand may include an amine-based compound.

The sulfur precursor has no particular limit but may be appropriatelyselected. Examples of the sulfur precursor may include hexane thiol,octane thiol, decane thiol, dodecane thiol, hexadecane thiol, mercaptopropyl silane, sulfur-trioctylphosphine (S-TOP),sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP),sulfur-trioctylamine (S-TOA), sulfur-octadecene (S-ODE),bis(trimethylsilyl) sulfide, or a combination thereof, but is notlimited thereto.

An amount of each component of the fourth solution (e.g., a second zincprecursor, a sulfur precursor, a ligand, and the like) may beappropriately selected by considering, e.g., based on, a composition, athickness, and the like of a desired shell.

The fourth solution is heated at a shell-forming temperature and thusforms a shell including a second semiconductor material including zincand sulfur on the core. The obtained semiconductor nanocrystal particlemay show the above composition/structure and photoluminescenceproperties.

The shell-forming temperature may be appropriately selected byconsidering, e.g., based on, a shell thickness, composition, and thelike. For example, the shell-forming temperature may be greater than orequal to about 200° C., for example, greater than or equal to about 210°C., greater than or equal to about 230° C., greater than or equal toabout 240° C., greater than or equal to about 250° C., greater than orequal to about 260° C., greater than or equal to about 270° C., greaterthan or equal to about 280° C., greater than or equal to about 290° C.,greater than or equal to about 300° C., greater than or equal to about310° C., greater than or equal to about 315° C., greater than or equalto about 316° C., greater than or equal to about 317° C., greater thanor equal to about 318° C., and greater than or equal to about 319° C.The shell-forming temperature may be, for example, less than or equal toabout 360° C., less than or equal to about 350° C., less than or equalto about 340° C., less than or equal to about 330° C., and less than orequal to about 325° C. The shell-forming time may be appropriatelyselected by considering, e.g., based on, a shell thickness, composition,and the like.

After the completion of the reaction, a nonsolvent may be added to areaction product and thereby nanocrystal particles coordinated with theorganic ligand compound may be separated. The nonsolvent may be a polarsolvent that is miscible with the solvent used in the core formationand/or shell formation reactions and is not capable of dispersing theproduced nanocrystals therein. The nonsolvent may be selected depending,e.g., based, on the solvent used in the reaction and may be for exampleacetone, ethanol, butanol, isopropanol, ethanediol, water,tetrahydrofuran (THF), dimethylsulfoxide (DMSO), diethylether,formaldehyde, acetaldehyde, ethylene glycol, a solvent having a similarsolubility parameter to the foregoing solvents, or a combinationthereof. The nanocrystal particles may be separated via centrifugation,sedimentation, chromatography, or distillation. The separatednanocrystals may be added to a washing solvent and washed, if desired.Types of the washing solvent are not particularly limited and may have asimilar solubility parameter to that of the ligand and may, for example,include hexane, heptane, octane, chloroform, toluene, benzene, and thelike.

In an embodiment, an electronic device includes the semiconductornanocrystal particle(s). The device may include a display device, alight emitting diode (LED), an organic light emitting diode (OLED), asensor, a solar cell, an image sensor, or a liquid crystal display(LCD), but is not limited thereto. In an embodiment, the electronicdevice may be a photoluminescence element (e.g., a lighting such as aquantum dot sheet or a quantum dot rail, a liquid crystal display (LCD))or an electric field light emitting element (e.g., a QD LED).

In a non-limiting embodiment, the electronic device may be an electricfield light emitting element. The electronic device may include a firstelectrode and a second electrode facing each other and a quantum dotemission layer disposed between the first electrode and the secondelectrode and including a plurality of quantum dots. The plurality ofquantum dots includes the blue light emitting semiconductor nanocrystalparticle. The electronic device may include an auxiliary layer (e.g., anelectron auxiliary layer such as an electron transport layer or a holeauxiliary layer such as a hole transport layer) including ZnO betweenthe first electrode and the quantum dot emission layer or between thesecond electrode and the quantum dot emission layer.

A device according to an embodiment is shown in FIG. 1. Hereinafter, thefirst electrode is referred to as an anode 1 and the second electrode isreferred to as a cathode 5, but they are not limited thereto.

The cathode 5 may include an electron injection conductor having a lowwork function. The anode 1 may include a hole injection conductor havinga relatively high work function. The electron/hole injection conductormay include a metal-based material (aluminum, magnesium, tungsten,nickel, cobalt, platinum, palladium, calcium, LiF, and the like) (e.g.,a metal, a metal compound, an alloy, a combination thereof), a metaloxide such as gallium indium oxide or indium tin oxide, or a conductivepolymer such as polyethylene dioxythiophene (e.g., having a relativelyhigh work function), but is not limited thereto.

At least one of the first electrode and the second electrode may be alight transmitting electrode or a transparent electrode. In anembodiment, both of the first electrode and the second electrode may belight transmitting electrodes. The electrode(s) may be patterned.

The light transmitting electrode may be made of, for example atransparent conductor such as indium tin oxide (ITO) or indium zincoxide (IZO), gallium indium tin oxide, zinc indium tin oxide, titaniumnitride, polyaniline, or LiF/Mg:Ag, or a metal thin film of a thinmonolayer or multilayer, but is not limited thereto. When one of thefirst electrode and the second electrode is a non-light transmittingelectrode, it may be made of, for example, an opaque conductor such asaluminum (Al), a lithium aluminum (Li:Al) alloy, a magnesium-silveralloy (Mg:Ag), or a lithium fluoride-aluminum (LiF:Al).

The light transmitting electrode may be disposed on a transparentsubstrate (e.g., insulating transparent substrate). The substrate may berigid or flexible. The substrate may be a plastic, glass, or a metal.

Thicknesses of the electrodes (first electrode and/or second electrode)are not particularly limited and may be selected considering deviceefficiency. For example, the thickness of the electrode may be greaterthan or equal to about 5 nm, for example, greater than or equal to about50 nm. For example, the thickness of the electrode may be less than orequal to about 100 micrometers (μm), less than or equal to about 10 μm,less than or equal to about 1 μm, less than or equal to about 900 nm,less than or equal to about 500 nm, or less than or equal to about 100nm.

The quantum dot emission layer 3 includes a plurality of quantum dots.The plurality of quantum dots includes the blue light emittingsemiconductor nanocrystal particle according to the embodiments. Thequantum dot emission layer may include a monolayer of the blue lightemitting semiconductor nanocrystal particles.

The electronic device may include charge (hole or electron) auxiliarylayers 2 and 4 between the anode 1 and the cathode 5. For example, theelectronic device may include a hole auxiliary layer 2 or an electronauxiliary layer 4 between the anode and the quantum dot emission layerand/or between the cathode and the quantum dot emission layer. (refer toFIG. 2)

The hole auxiliary layer may include for example a hole injection layer(HIL) to facilitate hole injection, a hole transport layer (HTL) tofacilitate hole transport, an electron blocking layer (EBL) to inhibitelectron transport, or a combination thereof, but is not limitedthereto. For example, the hole injection layer (HIL) may be disposedbetween the hole transport layer (HTL) and the anode. For example, theelectron blocking layer may be disposed between the emission layer andthe hole transport (injection) layer, but is not limited thereto.

A thickness of each layer of the hole auxiliary layer(s) may bedesirably selected. For example, each thickness of the layer may beabout 20 nm to about 50 nm, but is not limited thereto.

The electron auxiliary layer may include for example an electroninjection layer (EIL) to facilitate electron injection, an electrontransport layer (ETL) to facilitate electron transport, a hole blockinglayer (HBL) to inhibit hole transport, or a combination thereof, but isnot limited thereto.

For example, the electron injection layer may be disposed between theelectron transport layer and the cathode. For example, the hole blockinglayer may be disposed between the emission layer and the electrontransport (injection) layer, but is not limited thereto. A thickness ofeach layer of the electron auxiliary layer(s) may be desirably selected.For example, each thickness of the layer may be about 20 nm to about 50nm, but is not limited thereto.

The quantum dot emission layer may be disposed in the hole injection (ortransport) layer or an electron injection (or transport) layer. Thequantum dot emission layer may be disposed between the hole auxiliarylayer and the electron auxiliary layer.

The charge auxiliary layer, the electron blocking layer, and the holeblocking layer may include for example an organic material, an inorganicmaterial, or an organic/inorganic material. The charge auxiliary layer,the electron blocking layer, and the hole blocking layer may include forexample an organic material, an inorganic material, or anorganic/inorganic material.

The hole injection and/or transport layers may, each independently,include for example poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS),poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB),polyarylamine, poly(N-vinylcarbazole), polyaniline, polypyrrole,N,N,N,N′,N′-tetrakis (4-methoxyphenyl)-benzidine (TPD),4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA(4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine),4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA),1,1-bis[(di-4-tolylamino)phenylcyclohexane (TAPC), a p-type metal oxide(e.g., NiO, WO₃, MoO₃, etc.), a carbon-based material such as grapheneoxide, or a combination thereof, respectively, but are not limitedthereto.

The electron blocking layer (EBL) may include for examplepoly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS),poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB)polyarylamine, poly(N-vinylcarbazole), polyaniline, polypyrrole,N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (TPD),4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA,4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA), or a combinationthereof, but is not limited thereto.

The electron transport layer (ETL) may include for example1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA), bathocuproine(BCP), tris[3-(3-pyridyl)-mesityl]borane (3TPYMB), LiF, Alq₃, Gaq₃,Inq₃, Znq₂, Zn(BTZ)₂, BeBq₂, an n-type metal oxide (e.g., ZnO, HfO₂,etc.), or a combination thereof, but is not limited thereto. The n-typemetal oxide may be crystalline. The n-type metal oxide may be(crystalline) nanoparticles. The electron transport layer (ETL) mayinclude crystalline ZnO nanoparticles.

The hole blocking layer (HBL) may include for example1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA), bathocuproine(BCP), tris[3-(3-pyridyl)-mesityl] borane (3TPYMB), LiF, Alq₃, Gaq3,Inq3, Znq2, Zn(BTZ)₂, BeBq₂, or a combination thereof, but is notlimited thereto.

In an embodiment, the anode may include a metal oxide-based transparentelectrode and the cathode may include a (conductive) metal (Mg, Al,etc.) (e.g., of a relatively low work function). For example, PEDOT:PSS,TFB, and/or a p-type metal oxide may be disposed as a hole auxiliarylayer (e.g., hole injection layer or hole transport layer) between thetransparent electrode and the emission layer, e.g., emissive layer.(see, FIG. 3)

In an embodiment, the cathode may include a metal oxide-basedtransparent electrode (e.g., ITO, FTO, etc.) and the anode may include ametal (e.g., Al, Au, Ag, etc.) of a relatively high work function.(Inverted structure) For example, an n-type metal oxide (ZnO) may bedisposed between the cathode and the emission layer as an electronauxiliary layer (e.g., an electron transport layer). MoO₃ or anotherp-type metal oxide may be disposed between the metal anode and thequantum dot emission layer as a hole auxiliary layer (e.g., a holetransport layer and/or hole injection layer). (see FIG. 4)

Hereinafter, specific examples are illustrated. However, these examplesare exemplary, and the present disclosure is not limited thereto.

EXAMPLES Analysis Method [1] Photoluminescence Analysis

Photoluminescence (PL) spectra of nanocrystals are obtained by using aHitachi F-7000 spectrometer at an irradiation wavelength of 372nanometers (nm).

[2] Ultraviolet (UV) Spectroscopy Analysis

A UV spectroscopy analysis is performed by using an Agilent Cary-5000spectrometer to obtain a UV-Visible absorption spectrum.

[3] Transmission Electron Microscope (TEM) Analysis

Transmission electron microscope photographs of the nanocrystals areobtained using an UT F30 Tecnai electron microscope.

[4] Inductively Coupled Plasma (ICP) Analysis

An inductively coupled plasma-atomic emission spectroscopy (ICP-AES)analysis is performed using Shimadzu ICPS-8100.

Synthesis is performed under an inert gas atmosphere unless particularlymentioned.

Example 1 [1] Production of InZnP Core

0.12 millimoles (mmol) of indium acetate, 0.36 mmol of zinc acetate, and1.08 mmol of palmitic acid are dissolved in a 1-octadecene solvent in a200 milliliter (mL) reactor, and the reactor is heated at 120° C. undervacuum. After one hour, an atmosphere in the reactor is converted intonitrogen. The reactor is heated at 150° C., a mixed solution of 0.1 mmolof tris(trimethylsilyl)phosphine (TMS₃P) and 1 mL of trioctylphosphineis rapidly put therein, and the mixture is reacted for 10 minutes. Thereaction solution is rapidly cooled down to room temperature, acetone isadded thereto, and the mixture is centrifuged, and a precipitateobtained therefrom is dispersed in toluene. Referring to a UV spectrumof the obtained InZnP semiconductor nanocrystal (a core), the core has aUV first absorption maximum wavelength of 360 nm and thus a diameter ofabout 1.6 nm.

[2] Formation of ZnS Shell

1.2 mmoL of zinc acetate and 2.4 mmol of oleic acid are dissolved in atrioctylamine solvent in a 200 mL reaction flask and then,vacuum-treated at 120° C. for 10 minutes. The flask is internallysubstituted with nitrogen (N₂) and then, heated up to 280° C.

Subsequently, the InZnP core according to Reference Example 1 is rapidlyadded thereto, 0.01 mmol of S/TOP is added thereto, and the mixture isheated up to 320° C. and reacted to form a shell for 60 minutes.

The reaction solution is rapidly cooled down to room temperature,acetone is added thereto, and the mixture is centrifuged to obtain aprecipitate, and the precipitate is dispersed in toluene. FIG. 5 shows aUV-vis spectrum of the obtained InZnP semiconductor nanocrystal. TheInZnP semiconductor nanocrystal has a UV first absorption maximumwavelength of 400 nm.

[3] Analysis

Photoluminescence properties of the produced semiconductor nanocrystalare analyzed, and the results are shown in FIG. 6 and Table 1.Inductively coupled plasma-atomic emission spectroscopy of thesemiconductor nanocrystal particle is performed, and the result is shownin Table 1.

A transmission electron microscope analysis of the semiconductornanocrystal is performed, and the result is shown in FIG. 7. A TEM imageof the semiconductor nanocrystal is used to measure a particle size, anda distribution of the semiconductor nanocrystal is shown in FIG. 8.Referring to FIG. 8, the produced semiconductor nanocrystal has anaverage particle size of 3.5 nm.

Example 2 [1] Production of InZnP Core

An InZnP core is prepared according to the same method as Example 1except for increasing the reaction time into 15 minutes at 200° C. afterputting TMS₃P therein. Referring to a UV spectrum of the obtained InZnPsemiconductor nanocrystal (a core), the core has a UV first absorptionmaximum wavelength of 412 nm and thus, a diameter of about 1.9 nm.

[2] Formation of ZnS Shell

A shell-forming reaction is performed in the same method as Example 1except for using the core according to [1].

[3] Analysis

Photoluminescence properties of the produced semiconductor nanocrystalare analyzed, and the results are shown in FIG. 6 and Table 1.Inductively coupled plasma-atomic emission spectroscopy of thesemiconductor nanocrystal particle is performed, and the result is shownin Table 1.

Comparative Example 1 [1] Production of InZnP Core

An InZnP core is prepared according to the same method as Example 1except for using 0.2 mmol of zinc acetate and 0.76 mmol of palmiticacid. Referring to a UV spectrum of the obtained InZnP semiconductornanocrystal (the core), the core has a UV first absorption maximumwavelength of 398 nm and thus a diameter of about 1.8 nm.

[2] Formation of ZnS Shell

A shell-forming reaction is performed in the same manner as in Example 1except for using the core prepared according to [1].

[3] Analysis

UV-Vis absorption characteristics and photoluminescence properties ofthe semiconductor nanocrystal are analyzed, and the result is shown inFIG. 6 and Table 1. Inductively coupled plasma-atomic emissionspectroscopy of the semiconductor nanocrystal particle is performed, andthe result is shown in Table 1.

TABLE 1 PL, Full Width UV absorption at Half Maximum Mole ratio relativeto In wavelength (FWHM) QY (ICP-AES) Samples (nm) (nm) (%) P S Zn InComparative 398 464, 75 21 0.88:1 16.4:1 21.7:1 1.0:1 Example 1 Example1 395 451, 64 41 0.82:1 26.6:1 30.4:1 1.0:1 Example 2 412 461, 56 600.59:1 25.7:1 31.5:1 1.0:1

Referring to the results of Table 1, the semiconductor nanocrystalparticles according to Examples 1 and 2 show remarkably improved quantumefficiency and a narrow full width at half maximum (FWHM) compared witha quantum dot according to Comparative Example 1 in a blue lightemitting region.

Example 3: Manufacture of Device 1

A device (indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)(PEDOT):poly(styrene sulfonate)(PSS)/poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine)(TFB)/quantum dot(QD)/ET204(8-(4-(4,6-di(naphthalen-2-yl)-1,3,5-triazin-2-yl)phenyl)quinolone):8-quinolinolatolithium (Liq)(1:1)/Liq/Al) shown in FIG. 9 is manufactured by using thesemiconductor nanocrystal particle according to Example 1.

Specifically, an ITO electrode is deposited on a substrate, andPEDOT:PSS and TFB layers are respectively spin-coated thereon. On theTFB layer, a dispersion of a quantum dot in octane is spin-coated. Anorganic electron transport layer (ETL, ET204:Liq) is formed through avacuum deposition, and then, an Al electrode is deposited thereon.

Electroluminescence properties of the device are measured by applying avoltage (0 to 7 volts (V)) between the ITO electrode and the Alelectrode. Device properties are shown in FIGS. 10, 11, 12, and 13.Referring to the figures, a blue light emitting device using InP QD isrealized.

Example 4

In Example 1, a device(ITO/ZnO/QD/4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA)/MoO₃/Ag)shown in FIG. 14 by using the semiconductor nanocrystal particle ismanufactured in the following method. Electroluminescence properties ofthe device are measured by applying a voltage (0 to 7 V) between the ITOelectrode and the Ag electrode. Device properties are shown in FIGS. 15,16, 17, and 18. Referring to FIGS. 15-18 and 10-13, the device ofExample 4 uses ZnO but shows the same blue electro-luminescence as thedevice using an organic ETL according to Example 3 and improved colorpurity compared with that of Example 3.

The device is manufactured by spin-coating ZnO on ITO, and then, QD,hole transport layer (HTL), and an electrode are similarly deposited tothose of Example 3.

While this disclosure has been described in connection with what ispresently considered to be practical example embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A semiconductor nanocrystal particle, comprisingindium, zinc, and phosphorus, wherein a mole ratio of the zinc relativeto the indium is greater than or equal to about 25:1, and thesemiconductor nanocrystal particle comprises a core, the core comprisinga first semiconductor material comprising indium, zinc, and phosphorus,and a shell disposed on the core, the shell comprising a secondsemiconductor material comprising zinc and sulfur.
 2. The semiconductornanocrystal particle of claim 1, wherein the semiconductor nanocrystalparticle emits blue light having a maximum peak emission at a wavelengthof less than or equal to about 470 nanometers, and the semiconductornanocrystal particle has quantum efficiency of greater than or equal toabout 40%.
 3. The semiconductor nanocrystal particle of claim 1, whereinthe mole ratio of the zinc relative to the indium is greater than orequal to about 29:1.
 4. The semiconductor nanocrystal particle of claim1, wherein the semiconductor nanocrystal particle has a mole ratio ofthe sulfur relative to the indium of greater than or equal to about18:1.
 5. The semiconductor nanocrystal particle of claim 1, wherein thesemiconductor nanocrystal particle has a mole ratio of the phosphorusrelative to the indium of less than about 1:1.
 6. The semiconductornanocrystal particle of claim 1, wherein the zinc in the core is in acrystal lattice of InP.
 7. The semiconductor nanocrystal particle ofclaim 1, wherein the first semiconductor material comprises InZnP andthe second semiconductor material comprises ZnS.
 8. The semiconductornanocrystal particle of claim 1, wherein the semiconductor nanocrystalparticle has an average size of less than or equal to about 4.5nanometers.
 9. The semiconductor nanocrystal particle of claim 1,wherein the semiconductor nanocrystal particle has an average size ofless than or equal to about 4 nanometers.
 10. The semiconductornanocrystal particle of claim 1, wherein the core has a size of lessthan or equal to about 2 nanometers.
 11. The semiconductor nanocrystalparticle of claim 1, wherein the shell does not comprise selenium. 12.The semiconductor nanocrystal particle of claim 1, wherein thesemiconductor nanocrystal particle emits blue light having a maximumpeak emission at a wavelength of about 440 nanometers to about 470nanometers.
 13. The semiconductor nanocrystal particle of claim 1,wherein the semiconductor nanocrystal particle has quantum efficiency ofgreater than or equal to about 45%.
 14. The semiconductor nanocrystalparticle of claim 1, wherein a maximum peak emission of the blue lighthas a full width at half maximum of less than or equal to about 60nanometers.
 15. A method of producing a cadmium-free semiconductornanocrystal particle emitting blue light, comprising heating a firstsolution comprising an indium precursor, a first zinc precursor, a firstorganic ligand, and a first organic solvent at a first temperature ofgreater than or equal to about 100° C. and less than about 180° C.;adding a phosphorus precursor to the first solution to obtain a secondsolution; heating the second solution at a second temperature of greaterthan or equal to about 180° C. and less than or equal to about 260° C.to synthesize a core comprising a first semiconductor materialcomprising indium, phosphorus, and zinc; separating the core from thesecond solution; heating a third solution comprising a second zincprecursor, a second organic ligand, and a second organic solvent to athird temperature that is less than a shell-forming temperature, toobtain a heated third solution; adding the separated core and a sulfurprecursor to the heated third solution to obtain a fourth solution; andheating the fourth solution at a shell-forming temperature to form ashell on the core, the shell comprising a second semiconductor materialcomprising zinc and sulfur.
 16. The method of claim 15, wherein theindium precursor comprises indium acetate, alkylated indium, indiumhydroxide, indium chloride, indium oxide, indium nitrate, indiumsulfate, or a combination thereof, and the first zinc precursor and thesecond zinc precursor are the same or different and independentlycomprise a Zn metal powder, ZnO, an alkylated Zn compound, a Znalkoxide, a Zn carboxylate, a Zn nitrate, a Zn perchlorate, a Znsulfate, a Zn acetylacetonate, a Zn halide, a Zn cyanide, a Znhydroxide, or a combination thereof, the first organic ligand and thesecond organic ligand are the same or different and independentlycomprise RCOOH, RNH₂, R₂NH, R₃N, RSH, RH₂PO, R₂HPO, R₃PO, RH₂P, R₂HP,R₃P, ROH, RCOOR′, RPO(OH)₂, RHPOOH, R₂POOH, or a combination thereof,wherein R and R′ are independently a substituted or unsubstituted C1 toC40 aliphatic hydrocarbon, a C6 to C20 aromatic hydrocarbon, or acombination thereof, and the phosphorus precursor comprisestris(trimethylsilyl) phosphine, tris(dimethylamino) phosphine,triethylphosphine, tributylphosphine, trioctylphosphine,triphenylphosphine, tricyclohexylphosphine, trimethyl indium, or acombination thereof.
 17. The method of claim 15, wherein in the firstsolution, a mole ratio of the first zinc precursor relative to theindium precursor is greater than or equal to about 1.7:1.
 18. Anelectronic device comprising a first electrode and a second electrodefacing each other; and a quantum dot emission layer disposed between thefirst electrode and the second electrode, the quantum dot emission layercomprising a plurality of semiconductor nanocrystals, wherein theplurality of semiconductor nanocrystals comprises the semiconductornanocrystal particle of claim
 1. 19. The electronic device of claim 18,wherein the electronic device comprises an auxiliary layer comprisingZnO between the first electrode and the quantum dot emission layer orbetween the second electrode and the quantum dot emission layer.